Book Image

Learning Functional Programming in Go

By : Lex Sheehan
Book Image

Learning Functional Programming in Go

By: Lex Sheehan

Overview of this book

Lex Sheehan begins slowly, using easy-to-understand illustrations and working Go code to teach core functional programming (FP) principles such as referential transparency, laziness, recursion, currying, and chaining continuations. This book is a tutorial for programmers looking to learn FP and apply it to write better code. Lex guides readers from basic techniques to advanced topics in a logical, concise, and clear progression. The book is divided into four modules. The first module explains the functional style of programming: pure functional programming, manipulating collections, and using higher-order functions. In the second module, you will learn design patterns that you can use to build FP-style applications. In the next module, you will learn FP techniques that you can use to improve your API signatures, increase performance, and build better cloud-native applications. The last module covers Category Theory, Functors, Monoids, Monads, Type classes and Generics. By the end of the book, you will be adept at building applications the FP way.
Table of Contents (21 chapters)
Title Page
Credits
About the Author
Acknowledgments
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Y-Combinator re-examined


Let’s look at another Y-Combinator example in Go to improve our grasp of the topic. Remember the Fibonacci function in Chapter 1, Pure Functional Programming in Go? It looked like this:

func fib(x int) int {
if x == 0 {
return 0
} else if x <= 2 {
return 1
} else {
return fib(x-2) + fib(x-1)
    }
}

If it passes a 0, 1, or 2, it simply returns a value (0 or 1). Otherwise, it will call itself (recursion) with two functions that look like this--fib(x-2) + fib(x-1). Since values are continually being decremented by two or one, processing will eventually complete, at which time the accumulated values will be summed up.

The following diagram illustrates this recursive processing. The orange and red boxes highlight functions that only need to be executed once. Referential integrity allows us to store the value of those functions. Subsequent execution only needs to look up the stored value, rather than re-execute the function:

We define three function types in main.go, as...